OK sundialsvc4 , while I really appreciate your apparent attempts to lend a hand -- really.
This post is frankly frustrating. I pretty well alluded to the fact in my OP, as well as when I referenced a (DNS) resolver program I had written, that was IMHO pretty efficient (fast) returning hostnames, when fed a large number of IP's.

So, if I may be so bold; of course I'll be running a local DNS. In fact I have a whole DNS server farm I built/manage/run to accommodate this endevour, as well as all the domains, and associated services they entail.

So let us assume all of the above, when we're responding. K? :-)

Thanks :-)

--Chris